Bisphenol A (BPA) has been used for decades in a wide variety of consumer products, like metal food and beverage containers, thermal paper store receipts, and dental composites.

Though the FDA has found BPA safe after numerous studies, because it can exhibit hormone-like properties the public has grown concerned about conflicting claims. There have been studies that have found exposure of rodent fetuses, infants, children or adults can cause cause abnormalities, including cancer, as well as reproductive, immune and brain-behavior problems.

Researchers at the University of Missouri are now saying that daily exposure to very low concentrations of BPA by pregnant females can cause fetal abnormalities in primates.

"BPA is an endocrine disrupting chemical that has been demonstrated to alter signaling mechanisms involving estrogen, androgen and thyroid hormones," said Frederick vom Saal, Curators Professor of Biological Sciences. "Previous studies in rodents have demonstrated that maternal exposure to very low doses of BPA can significantly alter fetal development, resulting in a variety of adverse outcomes in the fetus. Our study is one of the first to show this also happens in primates."

Most studies involving BPA have been conducted on laboratory mice and rats and weren't methodologically valid, leading U.S. regulatory agencies to call for studies in primates. With funding provided by the National Institute of Environmental Health Sciences (NIEHS), vom Saal and colleagues studied the chemical's blood levels in pregnant female rhesus monkeys and their fetuses, which are more similar to human fetuses than rats are.

Frederick vom Saal and colleagues say that BPA can cause fetal and hormonal imbalances in primates. Credit: University of Missouri News Bureau

After collecting tissue samples, other researchers analyzed the tissues to determine if dBPA exposure was harmful to fetal development. Researchers found evidence of significant adverse effects in mammary glands, ovaries, brain, uterus, lung and heart tissues in BPA exposed fetus when compared to fetuses not exposed to BPA. The abnormalities were caused by levels of BPA in the monkey fetuses that were very similar to levels reported in previous studies of BPA in human fetuses.

"The very low-level exposure to BPA we delivered once a day to the rhesus monkeys is far less than the BPA levels humans are exposed to each day, which reflects multiple exposures," vom Saal said. "Our findings suggest that traditional toxicological studies likely underestimate actual human exposure and show, unequivocally, that biologically active BPA passes from the mother to the fetus. Additionally, our latest study shows that BPA causes damage to developing systems of monkey fetuses, and this is of great concern for human fetuses."

While the study itself may have been reasonably well conducted, a fundamental flaw in the authors interpretation has to do with this statement from the article above: "The very low-level exposure to BPA we delivered once a day to the rhesus monkeys is far less than the BPA levels humans are exposed to each day..."

Welll, actually the level tested is more than 4,000 times greater than typical human exposure to BPA (400 micrograms/kg tested versus < 0.1 micrograms/kg typical human exposure). These researchers make the same mistake made by many others, as discussed in my recent article on this exact topic http://www.science20.com/steve_hentges/close_enough_niehs_work-129098).

Specifically, they rely on reported levels of BPA in human blood that are considered by the world's experts in the field to most likely be the result of sample contamination, not indicative of actual human exposure (see the clear comments from authoritative experts on this point in my recent article). Since BPA is a common chemical, sample contamination at the ultra-trace levels reported in some human blood studies can easily happen and has been well demonstrated.

The authors seem to be well aware of this problem since they used deuterated-BPA in their own study for the reason in their words: "thus eliminating concern about potential BPA contamination from materials used in the preparation, handling or shipment of samples." Deuterated-BPA is a stable isotope form of BPA that would not naturally be present anywhere. So they eliminated the problem in their own lab, but selectively compare their results with other studies where the problem has not been eliminated. Accordingly, their interpretation of their results doesn't hold up.

... and why is there an issue regarding the reported levels of BPA in humans? Is there no scientific consensus regarding methodology and metrics?

You claim that the world's experts say not likely, so one is forced to ask ... who is doing research:? The world's amateurs?

Again, as with so many such controversies it seems that the lines are being drawn, not based on scientific data that may actually be considered "settled", but rather around agendas that seem to promote personal viewpoints.